1. Field of the Invention
This invention relates to improvements in fluid control devices and more particularly, but not by way of limitation, to a fluid level control apparatus.
2. Description of the Prior Art
There are many fluid systems wherein holding tanks, or the like are provided for storage of a supply or reservoir of the fluid. In these installations it is usually necessary or desirable to control both the upper and lower limits of the fluid level within the fluid reservoir. One widely used fluid level control method at the present time is to provide first and second valve control means in communication with the interior of the holding tank, one of the valve controls being responsive to the rising of the fluid level within the tank for stopping the introduction of the fluid thereto, and the other of the valve controls being responsive to the lowering of the fluid level within for stopping the withdrawal of the fluid and reinstating the introduction of the fluid thereto. Another widely used method of fluid level control comprises a float valve, or the like, sensative to relatively small fluctuations in the fluid reservoir for alternately stopping and starting the flow of the fluid thereto in order to maintain a substantially constant level within the tank. These methods have certain disadvantages in that the first mentioned method requires two complete valve assemblies which increases the overall cost of both the initial installation and the maintenance of the equipment. The second mentioned method results in a substantially constant on-off of the pumping equipment and other auxiliary apparatus with the fluctuation of the fluid level which results in considerable wear on the equipment.
Devices have been developed for sensing two different fluid levels within a reservoir, such as that shown in the Thorn et al U.S. Pat. No. 4,031,638, issued Mar. 28, 1978, and entitled "Level Control with Float Actuated Switch." This device includes two float members interconnected to travel together in a manner for activating a switching unit to stop the supply of fluid at a selected high level and to reestablish the supply at a selected low level. The vertical distance between the float members of the Thorn et al control apparatus determines the difference in the pre-selected high and low fluid levels to be monitored thereby, and it is readily apparent that the interconnection between the two float members limits the practical distance which may be established between the two floats. Thus, the frequency of the actuation of the pumping equipment and other auxiliary equipment required for maintaining these two fluid levels exerts undue wear on the equipment.